Melson testified that he initially didn't believe CBS' original reports exposing the allegations that ATF allowed thousands of high-powered weapons to cross into Mexico. But Melson told investigators when he reviewed documents relating to one specific case, he found what he called "a smoking gun." According to a partial transcript of Melson's testimony to Congressional investigators, "interdiction could have occurred, and probably should have occurred, but did not occur."

According to Rep. Darell Issa (R-CA) and Sen. Charles Grassley (R-IA) who've been investigating the gunwalking controversy, Melson told them he turned his findings over to the Department of Justice's Deputy Attorney General, James Cole.

However, Melson was sharply critical of the DOJ's response to news reports about the allegations and investigations by Congress. "The Department is really trying to find a way to push the information away from their political appointees."